This invention relates to pneumatic tires with tread belts and more particularly to an improved removable tread belt pneumatic tire constructed of a removable tread belt mounted on a radially reinforced beaded tire carcass that is typically for use with earthmoving vehicles.
The tread belt pneumatic tires of the present invention are generally designed for use on large earthmover vehicles and are subjected to high stress and loads under harsh environmental conditions such as in rock quarries, mines, foundries, and other areas where tires are subjected to puncture-producing and wear-inducing conditions.
As discussed in U.S. Pat. No. 4,351,380, certain prior art tread belt tire assemblies comprise a plurality of ground-engaging shoes spaced about the periphery of the supporting structure. The heavy loads on the shoes result in great stresses being developed that sometimes lead to premature tire failure. The U.S. Pat. No. 4,351,380 patent is directed to an improved track belt assembly which comprise a plurality of shoes spaced about the periphery of a load-supporting structure and secured to a reinforcing belt structure disposed on the side of the shoe opposite the ground-engaging side thereof
The large pneumatic tires, which are typically used for earthmoving vehicles, sometimes fail due to the high stress and loads caused by the harsh environmental conditions in which they are operated. These large prior art pneumatic tires had a greater tendency to fail in one of three tire locations or areas. The first problem area was that the turn-up end of the ply would sometimes break through the sidewall of the tire. A second problem area was a tire failure in the bead area. The third problem area was a tendency to fail in the crown and/or shoulder area of the tire.
In the prior art, conventional solutions to these problems include increasing the gauge of the sidewall to increase the bending stiffness, increasing bead area stiffness and robustness, and decreasing tire deformation under load by increasing the sidewall stiffness. To further improve tire durability, the ply turn-up portion of tires was typically reinforced.
In U.S. Pat. No. 4,609,023, having a common assignee with the present invention, the sidewall inserts were incorporated in the tire carcass to allow the ply structure to conform to its natural shape when the tire is inflated.
The most relevant prior art patent, U.S. Pat. No. 4,050,495, issued Sep. 27, 1977, teaches the use of a removable tread belt installed as an annular belt about the circumference of a tire carcass. The tread belt included laterally extending bars encapsulated in a matrix of rubber. The ends of the bars extended outwardly to a point beyond the widest portion of the carcass sidewall. The tread belt was rigidly supported by the bars at the ends of the tread belt to prevent deflection of the overhanging and otherwise unsupported tread belt at the lateral ends.
With the continual drive to improve earthmover performance, there is a continuing need to provide novel methods and tire designs for improving earthmover tire durability. The present invention is directed to an improved pneumatic tire and removable tread belt assembly with which the frequency of premature tire failure is thought to be substantially reduced. The present invention is also directed to providing an improved pneumatic tire and tread belt assembly which is designed to allow large tires to be transported in several sections and then assembled at the construction site to ease the otherwise difficult problem of transporting the large tires, i.e. sometimes over 13 feet in height and approximately 8,000 to 15,000 pounds. Moreover, the present invention relates to an improved pneumatic tire and removable tread belt assembly with which the driving characteristics of the tire can be more economically changed and the inventory of the number of tire spares that are typically needed can be reduced.
It is an object of the present invention to provide a pneumatic tire for an earthmover vehicle, the pneumatic tire being as defined in one or more of the appended claims and, as such, having the capability of being constructed to accomplish one or more of the following subsidiary objects.
It is another object of the present invention to provide an improved tire and removable tread belt assembly for an earthmover vehicle wherein the frequency of premature tire failure has been substantially reduced.
Another object of the present invention is directed to providing an improved tire and removable tread belt assembly which is designed to allow large tires to be transported in several sections and then assembled at the delivery site.
Still another object of the present invention is to provide an improved tire and removable tread belt assembly with which the driving characteristics of the tire can be quickly and economically changed.
Yet another object of the present invention is to provide an improved tire and removable tread belt assembly with which the number of tire spares that are stored in inventory can be reduced.
Still another object of the present invention is to provide an improved tire and removable tread belt assembly with a unique tread belt that is restrained from expanding radially outwardly.
A further object of the present invention is to provide an improved tire and removable tread belt assembly wherein the tire treads will maintain a more flat tread profile which will improve tread life and durability.
A still further object of the present invention is to provide an improved tire and removable tread belt assembly wherein the belt is constructed to provide penetration protection.
In accordance with an embodiment of the invention a two-piece tire assembly is disclosed. The two-piece tire assembly has a removable tread belt for installing about the circumference of a tire carcass and a tire carcass having an inflated and unloaded outer circumferential surface having an axial dimension no greater than the axial width of the removable tread belt.
The tread belt has a pair of lateral ends each axially extending beyond the inflated unloaded carcass at the circumferential surface by a distance of at least 4% of carcass width as measured at the tread belt and carcass interface, and wherein the tread belt width is at least equal to or wider than the loaded deflected carcass width as measured at the outer circumferential surface of the carcass.
Each lateral end of the tread belt has a plurality of circumferentially extending substantially zero degree oriented cords in a first reinforcement layer and is radially inwardly flexible under load.
The tread belt preferably has a radially outer surface having a substantially flat tread arc radius R1 between the lateral ends extending from 50% to 75% of the tread belt axial width and a smaller tread arc radius R2 extending from each of the lateral ends to the first tread arc R1, the radially outer tread surface having a sloping surface extending from a tangency to R2 to a lateral end. The radial difference in the tread belt surface as measured at the centerline of the tread belt and each lateral end of the removable tread belt is about approximately 3 to 8% of the outside diameter as measured at the centerline of the tread belt.
The tread belt has a belt reinforcing structure radially outward of the circumferentially extending cords in the first reinforcement layer. The belt reinforcing structure has a pair of cross-plies and a radially outer ply having cords oriented substantially 90 relative to the circumferentially extending cords in a first reinforcement layer.